FILE - In this Jan. 20, 2015 file photo, a plume of steam billows from the coal-fired Merrimack Station in Bow, N.H. President Barack Obama on Monday, Aug. 3, 2015, will unveil the final version of ... more

FILE - In this Jan. 20, 2015 file photo, a plume of steam billows from the coal-fired Merrimack Station in Bow, N.H. President Barack Obama on Monday, Aug. 3, 2015, will unveil the final version of his unprecedented regulations clamping down on carbon dioxide emissions from existing U.S. power plants. The Obama administration first proposed the rule last year. Opponents plan to sue immediately to stop the rule's implementation. (AP Photo/Jim Cole, File) less